Apparatus for bending tubing



June 22, 1965 J. H. DOYLE 3,190,103

APPARATUS FOR BENDI-NG TUBING Filed Oct. 16, 1961 United States Patent r 3,190,103 I APPARATUS FOR BENDING TUBING James H. Doyle, Malden, 11]., assignor to Harper-Wyman Company, Chicago, 111., a corporation of Illinois Filed Oct. 16,1961, Ser. No. 145,040 j 3 Claims. (Cl. 772-388) This invention relates to a method of and apparatus for making bends in tubing.

It is an object of this invention to provide a method 3,190,103 Patented June-22, 1965 invention by a series of operations or steps, the first of forming in tubing a very sharp'bend characterized by an inner radiuswhich is substantially equal to zero.

Another object of the present invention is to form such sharp bends near one end of a length of tubing while preserving both the. uniform wall thickness and the uniform circular cross section of the tubing throughout, and thereby to produce a section of tubing highly suitable for use, for example, in forming venturi tubes for gas ranges. g It is afurther object to form such a bend 'in a length of tubing with one single bending operation, thereby eliminating the expense involvedrin using several bending and shaping operations.

A further object is the provision of new and improved apparatus for carryingout the abovereferred to method.

More particularly,itisi an object of the present invention quickly and cheaply to form such bends by first angularly trimming one end of a lengthof tubing, and then bending the tubing near the trimmed end. In brief, the method of the invention includes the, steps of trimming at least a substantial portion of one end of a length of tubing at an angle of between 30? to 60, preferably45". The said end of the tubing is then bent by placing it upon a thumb tip mandrel projecting from a mandrel block which surrounds the exterior of the tube. The projecting end of the tubing is clamped by a clamping block. The blocks are then rotated relative to each other about a point opposite the curvedpart of the thumb tip mandrel to bend the tubing 90. The mandrel blocks are so constructed, as with adjacent cutaway portions opposite thecurved portions of the thumb tip, so that the .blocks can be rotated the desired 90".

Further objects ofthe present invention will appear from the following description, taken with the accompanying drawing, in which:

FIG. 1 is a perspective view of a length of tubing in which a bend has been formed in accordance with this invention;

FIG. 2 is an elevational view of a length of tubing at a preliminary stage in my method of bending tubing; 7

FIG. 3 is an elevational view of an alternative form of a length of tubing at the preliminary stage;

FIG. .4 is an elevational'sectional view of the tube of 7 FIG. 2 and'of apparatus for forming the bend in the tubing; r I

FIG. 5 is an elevational view, partly in section, of the mandrel block, mandrel, and tubing of FIG. 4 taken along the line 5-5 of FIG. 4;

FIG. 6 is an elevational view, partly in section, of the clamping die, mandrel, and tubing of FIG. 4 taken along the line 66 of FIG. 4 preliminaryyto bending of the tube; and, j

FIG. 7 is an elevational sectional view of the apparatus and tube of FIG. 4 at the completion of the bending operation. 7

Having reference to the drawing, FIG. 1 illustrates a length of tubing which hasv been formed in accordance with my invention with a right angle bend 12 having an inner radius 13 substantially equal to zero. a

The sharp bend 12 is formed in a straight piece of tubing 14 of any desired length, in accordance with the It; has .been found that in order to prevent the tubing fromitearing during the bending operation, the plane of the trimmed'endof the tubing may vary between about 309' to 60 from a plane normal to the. axis ofthe pipe, an angle of about 45 being preferred. 1 Alternatively, as'in- FIG. 3, it has been found that the tubing may be trimmed somewhat lessthan completely, as at 18,with a small part of the original end of the tubing remaining, as at 20. This alternativebut still substantial trimmingzallows tubing to be conserved. I i

Referring to FIG. 4, the next step in the operation involves placing the trimmed length of tubing 14 in the I bending apparatus, shown generally at 2 2. This bending apparatus includes a mandrel block 24, a mandrel 26, andtwo cooperating clamping dies 28 and 30 that are rn'oveable to bend the tube..

The mandrel block 24'consists of two major portions,

32 and-'34. The portions areprovidedwith coaxial circular bores 36 and 38 of difierent diametersi lTh diameterof bore38 is slightlyxlarger than the'outside diameter of tubingl14, so that when the tubing is inserted into bore 38,as.is shown in FIG. 4,':it may move axially. .lThe diameter of bore 36 is such as to receive tightly the mandrel, which .may be additionally secured,

. pose of which will'be explainedin connection -with"the bending operation 5 r.

As shown 'in FIGS. 4 and 6,the .two cooperating clamping dies 28 and 30 are so constructed that when they are tightlypressed together by suitable means (not shown) they cooperate to define a circular bore 42 tightly securing the tube.; 1 Thus, itwill be s'een that when the two clamping dies 28 and 30 areseparated, it is possible to slide the tubing 14 to the left as viewed in FIG.

4 through the clamping dies 28 and 30. and "to insert the angularly trimmed edge 16 ot the tube. 14 a short distance into section 34 of mandrel block 24 so that the endportion of the tubing encircles a portion of the mandrel thumb tip 40. It will further be seen that when the two clamping dies are pressed together as in FIGS.

4 and 6, the'tubing 14 will be tightly held against further movement. The clamping blocks may be mounted in known manner onsuitable supporting structure 43'for movement between tube clamping andnon-clamping portions. 1

After the tubing 14 has been'so placed in the apparatus 22 and tightly fastened'by clampingdies 28 and 30, the next step comprises a relative rotation of the blocks, as by rotational displacement of clamping dies 28 and 30 and of the part of tubing 14 that is held by them 'fromthe position shown in FIG. 4 to theposition shown in FIG. 7.. By suitable means known to those skilled in the art the clamping dies 28 and 30 are arranged to rotate in a clockwise direction, as shown in the drawing, through an arc of about the point indicated by the letter a, as by rotation of the supporting structure 43. Mandrel block 24 and clamping die 30 are respectively provided with cooperating angularly 45 bevelled surfaces 44 and 46 to enable the clamping dies 28 and 30 to be rotated 90- relative to blockv 24. The point a in FIGS. 3 and 4 maybe seen to coincide with the inner radius of FIG. 1. 7

As shown in FIG. 7, the efiect of this rotational movementis to provide tubing 14 with a sharpelbow or bend 12 having substantially a zeroradius at the 7 having angularly .cut away inner bend 13. It will be seen that due to the support bores; 38 and 42 in the mandrel block 24 andin clampk ing dies 28 and 30, the parts of the tubing on either sidev of the. bend 12 are able to. retain their original cirgivento the outside of .the tubing '14 by the circular;

,cularcross section. It will furtherbe seen that the thumb tip 40. of mandrel 26. prevents the tubing from collapsing during the' bending operation and maintaining the circular cross section of the tubing at the bend. 7 Thus, itwil'l be appreciated that the initial angular.v trimming of the tubefld allows 'itto. be bent very .abruptly about the point. a (or 13) without'the tubing 14 tearing at the outside of the bend'12.

As ,canbe seen 'in FIGS. 1 and 7, the resulting bend 12 in the tubing 14 is characterized by. the fact that the inner radius of the bend 12 is substantially. equal to zero. In order to :achieve a .bend of this extreme shortness itflhas been found necessary to place the tubing 14 within apparatus 22' so that the .pointon tubing 14 which lies directly above point a is "along" the shortest length of the trimmed tube-14:andis spaced away from thei trimmed edge 16. of tube 14 a distance approximately equalv to, and not greater than, the radius of the tube.

" spaced a distance approximately. equal to. and not greater than the radius of the tube .from said short dimension,

4 r 2 surfaces adjacent said point permitting said blocks to be moved substantially 90 about said pointrelativei to. each other, thereby to form a bend having a substantially zero radius. 7

e 2. .Apparatus for producing a substantially zero radius bend in a length of tubing having'a substantial portion .at one end trimmed at an angle, said apparatus comprising a mandrel block having an opening-for slidably re-s ceiving the trimmed end of, the'tubing, a thumb tip mandrel positionedwithin said openi g and having a curvedtip portion extending beyond the mandrel block a distance corresponding substantially to the diameter of the tubing,

1 and clamping means for fixedlylcla'mping said tubing ad 'jacent saidmandrel bloicklin one position; said mandrel block and clampingmeans being rotatable with respect to one another'about a poinfon thetube o'pposite the curved portion of the thumb tip mandrel, said point lying along the short'dimension of the trimmedtube and trimmed end to. form a bend in said tubing having an inner radius of curvature at said point of substantially Inorder to prepare the bent .portion of tubing "10 for'its intended use it maybe removed from the bend ing apparatusiand-trimmed' or otherwise. finished, as.

known andrunderstoo'd by those skilled in the art.

, .It will be appreciated that this illustration of my in,

vention is simplified for clarity in .thestructureshown .herein. 'It is to be understood that in. actual. operation fully automatic means may be applied to the execution of my nethoduhere disclosed, and that'this-is within the, scope of my present invention. *iThe-drawing and the specification presented'herewith constitute a full disclosure of f my I improved method of bending tubing in such clear and exact terms as to enable any person skilled tives, equivalents and modificationsfmay be practiced without departing from the scope of the in'ventiomwhich V is defined by thefollowing claims. 7

What is. claimed astnew and desired to besecured by Letters Patent of the United States is; j

1; Apparatus for bending tubing to have substantially a zero radius, at the inside of the bend including a' man drel block having a tube receiving openingw atone end with a diameter slightly' greater than the [outside di'-' ameter of the tube and having concentrically disposed thereina thumb tip mandrel having a curved tip portion and an outside diameter slightly lessithan the inside diameter of the (tube and with its tip portion projecting a fixed distance from the mandrel block corresponding substantially to the diameter of the tube, whereby an t in the art topracticefthe invention Various alternar 9 end portionof the tubing may be slidably received in I said block, a tube encircling clamp block extending} in r a one position froma point. immediately adjacent the manin drel block and adapted fixedly closely to encircle and to hold tubing projecting from the mandrel block, said' mandrel and mandrel block andsaid clamp blockbeing relatively 'moveable'to bend said tubing around the thumb tip. mandrel abo'uta pointonthe tube opposite the curved -part. of the thumb tip mandrel, saidblocks abutting each,

other in said one p'osi tion before the tubeis bent and f 3. Apparatus for. producing a'substantially zero radius i bend in a length of tubing having asubstantial portion of one 'end trimmed at an angle. of about 45, said apparatus comprising a mandrel blockrhaving an open ing at one end with a diameter somewhat greaterthan: the outside diameter of thetubing, athumb tip mandrel fixedly mounted in said mandrel'block and disposed concentricall-y with respect to; said; openingtwherebythe trimmed end of said tubingmay be slidably inserted around said mandrel and into said opening until a point on the short dimension of'the tubing spaced a distance approximately equal to" and not greater: than the radius of the tubing from the sliortdimension' trimmed end. of the tubing lies'at thefrnouth of said openings-Said; mandrelhaving a curved tip portion extending beyond. said opening a; distance corresponding substantially" to the 'diameter of the tubing, and a tube encirclingclamping block disposed in one position immediately adjacent said mandrel block for fixedly and closely encirclingtuba ing projecting from said. mandrel block, said' mandrel and mandrel block and said-clamping block being-rotat "able through'90 with respect to one another 'fromsaid one position to draw said trimmed end of said tubing through said opening and to :bend said' tubing around the extending curved ti-p. portion of the mandrel abo u-t'said point on the short dimension vof the tubing;

Re renc s te y he V UNITED STATES PATENTS oHARL Es w. LANHAM,Primary Examiner; 5

WHITMORE A.w1Lrz, Examiner,

- Andres 15x40 

1. APPARATUS FOR BENDING TUBING TO HAVE SUBSTANTIALLY A ZERO RADIUS AT THE INSIDE OF THE BEND INCLUDING A MANDREL BLOCK HAVING A TUBE RECEIVING OPENING AT ONE END WITH A DIAMETER SLIGHTLY GREATER THAN THE OUTSIDE DIAMETER OF THE TUBE AND HAVING CONCENTRICALLY DISPOSED THEREIN A THUMB TIP MANDREL HAVING A CURVED TIP PORTION AND AN OUTSIDE DIAMETER SLIGHTLY LESS THAN THE INSIDE DIAMETER OF THE TUBE AND WITH ITS TIP PORTION PROJECTING A FIXED DISTANCE FROM THE MANDREL BLOCK CORRESPONDING SUBSTANTIALLY TO THE DIAMETER OF THE TUBE, WHEREBY AN END PORTION OF THE TUBING MAY BE SLIDABLY RECEIVED IN SAID BLOCK, A TUBE ENCIRCLING CLAMP BLOCK EXTENDING IN ONE POSITION FROM A POINT IMMEDIATELY ADJACENT THE MANDREL BLOCK AND ADAPTED FIXEDLY CLOSELY TO ENCIRCLE AND TO HOLD TUBING PROJECTING FROM THE MANDREL BLOCK, SAID MANDREL AND MANDREL BLOCK AND SAID CLAMP BLOCK BEING RELATIVELY MOVEABLE TO BEND SAID TUBING AROUND THE THUMB TIP MANDREL ABOUT A POINT ON THE TUBE OPPOSITE THE CURVED PART OF THE THUMB TIP MANDREL, SAID BLOCKS ABUTTING EACH OTHER IN SAID ONE POSITION BEFORE THE TUBE IS BENT AND HAVING ANGULARLY CUT AWAY SURFACES ADJACENT SAID POINT PERMITTING SAID BLOCKS TO BE MOVED SUBSTANTIALLY 90* ABOUT SAID POINT RELATIVE TO EACH OTHER, THEREBY TO FORM A BEND HAVING A SUBSTANTIALLY ZERO RADIUS. 